Electric vehicles such as an electric automobile, a hybrid automobile equipped with an internal combustion engine, and a fuel cell automobile equipped with a fuel cell are equipped with a battery apparatus for supplying electrical energy to an electric motor for driving the vehicle. The battery apparatus of this type includes a plurality of battery cells that are connected in series electrically. These battery cells emit heat produced in chemical reactions at the time of charging and discharging of the battery cells. It is important to suppress the increase in the temperature of the battery cells, for maintaining the operation characteristics of the battery apparatus, and avoiding the decrease in the product life of the battery apparatus.
In such a battery apparatus, for example, according to the technical concept disclosed in the pamphlet of International Publication No. WO2011/105256, a plurality of cooling elements (supports in the form of sponge, etc.) for absorbing insulating cooling liquid stored in a battery case with a predetermined space of the battery case unfilled with the cooling liquid, are brought into contact with each of the battery cells. The evaporation latent heat of the cooling liquid of the cooling element is utilized to cool the battery cells. In the battery apparatus, since the space inside the battery case is not fully filled with the cooling liquid, it is possible to achieve weight reduction of the battery apparatus. In the battery apparatus, the cooling elements are filled between the adjacent battery cells, and between the battery cell and the battery case.